2G Bad O2 sensor?

[rolltidero]

Recently I had my turbo replaced by a reputable shop that specializes in Mitsubishi (they were completely rebuilding the engine of an Evo VII while I was there). I have a narrowband A/F gauge. I know it sucks, it's useless, I need a wideband, blah blah blah, I get it but it was on the car when I got it.

Ever since I had the turbo replaced, the gauge has not worked (less than usual ). When I start it up it doesn't sweep at all. When I start driving, it lights up but doesn't move, then when I shift, it goes completely dark then lights up when I accelerate again. Even in neutral it is barely lit. I've checked and it is wired into the ECU instead of directly into the O2 sensor.

I'm not sure is that's whats wrong because I don't know how to check because I've never installed a gauge like this.

Also, since the turbo has been changed my MPG has been terrible. Before I would fill up at around 1/4 of a tank and I would get about 175-200 miles on 3/4 of a tank. Since the turbo has been replaced, I get about 100-125. Like I said I think it's the O2 sensor but I've also read that it could be the MAF. How do I check the O2 sensor (I don't have an O2 sensor socket)? Otherwise, what could be wrong? If this has already been covered I apologize.

PS: I have had no CEL either

 

[eclipsyco]

Either a bad MAF or a o2 sensor would throw a CEL is even your CEL working? When you turn on the ignition does it come on? Looks like you are running very rich do you smell gas o any black smoke from the tail pipe? Or could be a big boost leak assuming you are on a stock MAF!

 

[rolltidero]

Either a bad MAF or a o2 sensor would throw a CEL is even your CEL working? When you turn on the ignition does it come on? Looks like you are running very rich do you smell gas o any black smoke from the tail pipe? Or could be a big boost leak assuming you are on a stock MAF!

My CEL is working, it lights up when I put the key in the ignition. Little bit of a gas smell but not very strong. I have not noticed any black smoke and that's even with the top down. I had a little bit of white when I first got the car back because the previous owner had the boost turned up to 17 on the T-25 and it failed and dumped oil into the engine but even that smoke is gone now. Now I have the boost at 12-13 PSI. I didn't have any boost leaks before the replacement and that was only about 2 weeks ago.

 

[luv2rallye]

Testing O2 sensor: http://www.gnttype.org/techarea/ecmsensors/O2sensors.html